US2366567A - Process for executing catalytic conversions with regenerative contact masses - Google Patents

Description

2, 1945 "L l. SHULTZ 2,366,567 PROCESS FOR EXECUTING CATALYTIC CONVERSIONS WITH REGENERATIVE CONTACT MASSES Filed Jan. 29, 1940 3 Sheets-Sheet 1 Fi'gIn lnventor: lrvingl. Shirl 3 Sheets-Sheet 2 J Z, 1945 i. 'l. SHULTZ PROCESS FOR EXECUTING CATALYTIC CONVERSIONS WITH REGENERATIVE CONTACT MASSES Filed Jan. 29, 1940 Patented Jan. 2, 1945 CONVERSIONS CONTACT MASSES WITH REGENEBATIVE II'VingI. Shultz, Long Beach, Calif., assignor to Shell Development Company, San Francisco. Calif., a corporation of Delaware Application January 29, 1940, Serial No. 316,148

2 Claims.

The present invention relates to a process for executing catalytic conversions, particularly endothermic conversions, with the aid of regenerative contact masses and periodically restoring the efliciency of the contact mass in situ by passing a regenerating fluid therethrough. More particularly, the invention relates to the treatment of hydrocarbons with the aid of regenerative contact masses.

' The methods employed in the production and treatment of petroleum products have undergone marked changes and are still being constantly improved. At one time the desired hydrocarbon products were simply separated from the petroleum by simple methods, refined, and sold as such. This practice was more recently superseded or augmented by thermal treatments. By suitable thermal treatments (particularly thermal cracking) much larger yields of more valuable hydrocarbon fractions can be obtained and, in some instances, products of superior proper- I ties produced.

At the present time the efiorts of the industry are directed mainly towards the production of even better yields of further improved products by making use of various catalytic processes. These various catalytic processes fall under three main categories, namely synthesis, rearrangement and cracking. In the case of syntheses, the aim is to synthesize various desired hydrocarbons from lowmolecularweight materials, such as the lower olefins, the constituents of cracked and natural gas, etc. theses, such for instance as polymerization, alkylation, etc., nearly all involve exothermic reactions and can be conveniently carried out in many cases at low and moderate temperatures. Although much progress has been made with cat-. alytic syntheses, and processes for the productionof superior products from cracked gases,

etc., are now used to a considerable extent, the catalytic treatment of hydocarbon to produce various rearrangement and cracking reactions has not been so successful.

" processes is to carryout certain useful individualfl rearrangement and/or cracking reactions, -'most of which occurto' acertain extent in-ther- "*inal treatments, under closely"controlled condi- These reactions, since they are generally The aim in these tions.

The various 'synendothermic and usually require relatively high temperatures, are made much more difficult to carry out on a commercial scale.

There are, at the present time, two main meth- 5 od s for carrying out these various endothermic processes. Although a certain measure of success has been achieved by both methods in isolated cases, both methods possess certain inherent disadvantages which make their application very costly.

According to the first of these methods the hydrocarbon or other combustible fluidl to be treated is passed, usually in the vapor phase, through a suitable contact mass packed in. heated tubular reactors, Since, in this method, the

heat required must be introduced into the reaction zone through the reactor walls, metallic tubes of small diameter (usually less than 3- /2 in.) and considerable length must be employed.

This requires the use of a great number of tubes,

for instance, a plant capable of handling 1000 bbls. of feed per day would require over 250 tubes each 14 feet long; Furthermore, the tubes are quite expensive and must be frequently replaced since the only commercial materials so T far found which possess the necessary mechanical strength and heat conductivity and which are capable of withstanding the repeated changes in temperature and change from reducing condi- 0 tions (conversion period) to oxidizing conditions (regeneration period) are a few expensive alloy steels, and even these have only a very short life.

The time required for the length of the contact bed and is quite long when using such tubes; also many of the most desirable contactmasses are quickly poisoned 40 when employed in contact with the heated metal tubes. The other alternative method for executing such reactions is to pass the material to be treated, usually in the .vapor phase, in contact with a contact mass contained in a converter of relatively large dimensions. In this method the neoessary heat iseither supplied by heating tube embedded in the catalyst mass or periodb Cally ing the contact mass. This method,

while it has certain advantages over the abovedescribed method using tubes packed with con tact material, has inherent disadvantages which militate against its use. If the necessary heat is to be applied all or in part by suitable heating tubes embedded in the contact mass, it is necessary to circulate molten eutectic salt mixtures. This is very expensive and'troublesome and presents very great engineering difliculties. Furthermore, this method of heating can be applied only when employing certain particular contact materials which are not poisoned by contact with the metal heating tubes. If the heat is to be supplied by periodically heating the contact mass, the process cannot be executed under closely controlled conditions at the most desirable temperaturebut is executed at a varying temperature as the contact mass cools. This method also necessitates the use of very short conversion periods; it'also. entails considerable loss of time and the converter must be subjected to high vacuum after each conversion period in order to avoid excessive loss of material. Also, the regeneration takes place over a temperature range and consumes more time when this methad is applied. 7

I have invented and de proved method and apparatus for executing catalytic conversions of the type in question. When executing such conversion processes accordin to the present method most of the disadvantage inherent in the hitherto proposed methods are substantially avoided.

According to the present method, the contact mass is divided into a. plurality of separate beds .in a suitable reaction converter. to be treated is preheated outside of the converter .and led, preferably in the vapor phase,

The material consecutively-through the various beds of con-, tact material. After contacting the first portion of contact mass in the first bed, and before conconverter of the type illustrated in Figs. III

' and IV.

. the converter is separated by partitions 4. The

converter, as shown in Figs. I and II, i designed to be operated continuously with either the upper or lower three beds of contact mass on conversion while the otherthree beds are being reactivated. The converter is provided with a feed inlet 5 for the upper three beds, a feed inlet 6 for the lower three beds, a regeneratin fluid inlet 1 for the upper three beds, a regenerating fluid I inlet 8 for the lower threebeds, an outlet 9. for

eloped anew and imtacting each succeeding bed of contact mass,

. the partially converted material is withdrawn from the reactor and passed through suitable coils in a closely associated furnace wherein a desired quantity of heat is added. In the regeneration or reactivation step a conventional regenerating fluid is passed through the converter, an oxidizingfluid, such as air, is introduced into the upper three beds, anoutlet In for the lower three beds, inlets II to 16 for oxidizing fluid situatednear the head of each bed of contact mass, and connections 11-44 for'exterior coils by-passing the upper two and lower two partitions.

The connections I! and I8, I9 and 20, 2| and 22, and 23 and 24, are connected to coils 25, 28,

,2! and 28, respectively, in. a, suitable variable temperature furnace such as illustrated in Figs. V and VI. The furnace illustrated in Figs. V and VI is fired near the center and is provided with means 29 for deflecting the hot gases either up past coils 25 and 26 or down past coils 21 and 28. The furnace is furthermore provided with steam inlets 30 and 3|. These steam inlets are for the purpose of slightly cooling either section, of the furnace when the corresponding section of the converter is on regeneration and the hot gases are being deflected through the opposite section. I

The application-of apparatus of the general type illustrated in Figs. I, II, V and VI is illustrated by the flow diagram shown in Fi X. For

the purpose of illustration it is assumed that the upper four beds of catalyst mass in the converter are on conversion and that the lower four beds of contact mass are being regenerated. The. material to be treated is brought to approximately the desired reaction temperature and enters the converter through valve 50 above the upper- The process and apparatus of my invention, as well as certain modifications and embodi-' ments thereof, are described in more detail with reference to the attached drawings. Referring to the drawings, Flgsi I and II are horizontal and vertical sections respectively of one type of suitable converter. Figs. V and VI are horizontal and vertical sections of a variable temperature furnace adapted for use with a converter of the 'type illustrated in Figs. I and II. Fig. X is a flow diagram of a suitable arrangement of ap-.

paratus employing a converter of thetype illusmost bed of contact mass. In passing down through the upper bed of contact mass partial conversion is effected and the temperature of the material drops. After contacting theupper layer of contact mass, the partially converted and cooled material passes through the uppermost.

coil in the furnace wherein it is reheated to the desired temperature and returned to the converter to a point just below the uppermost partition. When the material has passed through all of the four layers of contact material in the upper section in this mannenit leave the converter via a pipe 3 is cooled in the cooler, and is finally withdrawn va a valved connection 33.

At the same time the four lower layers of contact mass are being regenerated. A regenerating fluid (for instance any inert gas such as combustion or flue gas) from the gas storage" 'vesselis led via pipe 34 in which there is an automatic pressure regulating valve 35 controlled by the low pressure side, heater 36, valve 31', and pipe 38 into the upper section above the four lower beds 2 of contact material. A controlled amount of oxithrough the-upper of the lower three coils in the lower section 'of the furnace wherein heat is withdrawn, and is then mixed with a second portion of oxidant entering via 42 and passes through the next lower layer of contact mass, etc. In or- -der to withdraw heat from the regenerating gas g 3 I04. At the lower part of the partition there is provided a device I05 for deflecting the hot gases to either side. Inlets I06 and I01 are also provided for introducing steam into the cooling side of the furnace.

The advantages which may be realized through the use of the apparatus and method of my invention are several and important. According to the present method of operation, beds of contact mass of relatively large cross-section allowing large throughput capacities may :be easily. employed.

in the coils in the lower section of the furnace,

the hot gases are deflected upward and a small amount of steam may, if desired, be introduced into the lower section of the furnace via a valved inlet 45. The spent regenerating fluid is withdrawn from the bottom of the converter via outlet 46 and the cooler, and is recirculated via pipe 41, the compressor and pipe 48 back to the storage tank. Excess spent regenerating medium beyond that required for recirculation, etc., is allowed to escape via a valved outlet, 60.

When it is desired to regenerate or reactivate the upper four catalyst layers, valves 31, 4l--45, 50 and -SI are closed; valves 5259 are opened,

- and the hot gases in the furnace are deflected regenerating medium meanwhile enters the converter via valve 52' at the top, passes in the described manner through the upper layers of con tact mass, and leaves the converter via outlet 32.

7 During the reactivation pfthe upper'section of the converter, an oxidant is introduced via valved inlets 54- 51, and steam may be injected into the furnace via valved inlet 53.

In many cases, especially when the conversion periods are relatively short and/or when the contact mass is particularly sensible to water vapors, it is desirable to flush the reactants from the system just prior to beginning the reactivation. When employing apparatus arranged as indicated in Fig. II, this may be done by passing a quantity of'the inert gas from the'gas storage through the system with the compressor stopped before opening the air inlets 54--51,(or 4i-44). The inert gas, after flushing the system of reactants, leaves via valved outlet 60.

Figs. III and IV illustrate a converter embodying the same principles but of somewhat different construction. In this converter the catalyst beds.

are divided into two sections by a vertical partition l0! such that the beds of contact mass on one sidemay be employed on conversion while the beds of contact mass on. the other side are being regenerated. 'The details of the converter are otherwise much the same as described with regards 'to Figs. I and II except that the horizontal partitions 4 of ,FlgFII are shown somewhat conical at I02 and are connected at their apices with the outlet pipes I03 which outletpipes leave the :converter from pointsbelow thepartition rather than above the partition as in" the converter showninFl slandII. Y J

Thus, for example, whereas a plant capable of treating 1000 bbls. of feed per day requires, in

general, about 270 three-inch tubes, each 14 feet long, this same throughput may be treated more efllciently according to'the invention in one small pliedto the reactants'outside-of the reaction chamber, and not through the converter walls, the converter may be lined with a'ce'ramic or other material which does not deteriorate readily, catalyze the form tion of carbomand poisonthe contact mass. e to the fact that the heat is supplied and withdrawn from the reactants in a plu rality of stages, only relatively mild heating and cooling-need be applied, and difficulties due to severe temperature changes in the reactor are avoided. This not only reducesthecost and upkeep of the converters but also minimizes other secondary difflculties whichare commonly encountered, such, for example,'as'the deposition of carbon and tars, the degradation lyst particles, etc.

Another advantage afforded by the present process is the economy with which the regeneration may be efiected. Since the catalyst is employed in a plurality of layers, the time required for reactivation may be maintained much. shorter than that possible when employing the conventional tubular type reactors: in fact, the reactivatio'n, under optimum conditions, i reduce by a factor which is approximately the reciprocal of the number of layers of catalyst reactivated. Furthermore, the cost of pumping the regenerating gas through the catalyst-requires considerable energy and always represents a substantial proportion of the reactivation costs; according to .The method and apparatus of my invention are also advantageous over the conventional methods in that they allow the materials to be treated under more favorable conditions. The adjust- -ment and control of the reaction conditions to meet the. demands'of the material treated has heretofore been given lnsufllcient'consideration.

One reason for this is "that 'the conventional methods of operation do not allow sufficient con-- trol of these conditions. If it is-desired to treat a certain material with a certain catalyst. the usual practice'is to pass the-material through the reactor at different conditions of space velocities and temperature and then choose those conditions which give the best results. does not establish the optimum conditions for;the reaction but only an average condition which is most practical of the catafor the particular apparatus in question. when employing the present method, however, it i possible to go further than this and establish and maintain conditions which are more nearly the optimum for the particular reaction in question. Thus, when treating a hydrocarbon in the presence of a regenerative contact mass, the composition and character of the material undergoes considerable change during it passage through the reactor. In some cases, for instance in certain catalytic cracking processes, the reaction products are much less stable than the reactant while in others, for instance in certain catalytic dehydrogenation processes, the reactants are much less stable than the reaction products. It is found that as a general rule, in executing reactions of the former type by conventional methods, the deposition of tars, etc., on the contact mass and the loss in activity incident thereto are predominantly in the first contacted portions of the contact mass, whereas in the processes of the lattertype such deposition and deactivation are largely confined to the last contacted portion of the contact mass. This is due to the fact that the conditions prevailing in the reaction zone are not adjusted according to the changing nature of the reactants, but are average over-all conditions.

assase'z According to the process of the present invention the conditions more nearly optimum for the particular ,reactants in question may be established and maintained by adjusting the thickness of catalyst beds and/or the amount of heat supplied to the reactants in the various coils. Thus the present process, may be applied in any of three ways, according to the nature 'of the reactants, the catalyst, and the reaction. In one embodiment of the invention the various catalyst beds are employed in substantially equal thickness and the coils are adjusted to give substantially equivalent heat transfer. By operating in this manner the reaction is carried out with an increasing temperature gradient. 7 This method of operation is usually most advantageous when executing conversions in which products of increased stability are produced. 1

According to a second embodiment of the invention the various catalyst beds are employed in substantially equal thickness and the coils are adjusted, for instance by their length or position, to supply an amount of heat approximately proportional to the temperature drop in the respective beds. When operating in this manner the E reaction is carried'out at a constant temperature; or, if desired, a somewhat decreasing temperature gradient. This method is usually most advantageous when executing conversions ,in

which products of lesser stability are produced,'.'

although it may-also be advantageous in certain cases for reactions of the former type.

When exec'utin a process according to one of these embodimen s, the conversions and temper-' ature drops in each succeeding layer of catalyst become'smaller. This is illustrated in the following table showing datarelating t0 the dehydrogenation of butane. Thepertinent data are:

Feed: 14% iso-butane and 86% n-butane Catalyst: 8-14 'rnesh alumina impregnated with 13-15% chromium as oxide Space velocity: 35 volumes of butane gas measured at standard conditions per volume of catalyst per minute Average conversion to butene: 30% Total depth} of catalyst bed; 4.5 feet According toa third embodiment'of the invention, coils adjusted to give substantially equiv-' alent heat transfer are employed and the thick- 1 ness of the various beds of contact mass are adjusted to provide a substantially equal temperature drop. By operating according to this method, the reaction may be executed at a constant or substantiallvfconstant temperature to efl'ect high conversions. It is most advantageous for conversions in which products of increased stability are produced.

When operating according to this embodiment. the conversions and temperature drops in the various layers of catalyst are approximately equal. This is illustrated"in the following table which also relates to the dehydrogenation of butane. The pertinent data are the same 'as given above.

most efficient and economical manner.

Table II Catalyst Depth of Butane an t: pttti. itlfi? gilt: come on contact inches percent 11 lo. 0 18 lo. 0 110 25 10.0 11

\ s s. 0 so 8 6. 0 66 6. 0 U6 12 U. 0 66 Q 17 6. 0 06 By adapting the apparatus to operate according to one of the three above 'speciflc modes, it is not only possible to adjust and maintain the conditions to suit the changing nature of the reaction mixture, but it is also possible to provide a uniform rate of decline otthe various catalyst beds. This is of considerable importance since it allows the reactivationto be eflected in the when executing a reaction wherein the deposi tion of carbonaceous matter normally occurs prev dominantly in that portion of the contact mass that is first-contacted, it is preferable either to employ contact beds of equal thickness and to maintain an increasing temperature gradient, or

to employ contact beds of progressively-increasing thickness. Beds of contact mass of progressively increasing thickness suitable for this latter mode of operation are shown in the converter illustrated in Figs. III and IV. By, adjusting the conditions for the particular circumstances as above described, the periodic reactivation of the contact 'mass may be carried out most efliciently and. in

the shortest possible time.

While the present process and apparatus be advantageously employed in the execution 08;-

. reaction conditions whereby a oxides or sulfides such as those of Cr, Mo, W, etc.,

may be used. In catalytic cracking, on the other hand, any of the conventional partially hydrated silica-alumina and silica-zirconia catalysts may, for example, be employed. Numerous other suitable regenerative catalysts which may be applied in the apparatusand method of the present invention are disclosed in detail in the scientific and patent literature relating to the various respective processes.

I have, in the foregoing, described my inven-- tion in its preferred embodiments and shown by illustration various apparatus suitable for the execution thereof. I am aware, however, that the described process and apparatus are capable of numerous variations and modifications which will be apparent to those skilled in the art. I'do not, therefore, by the specific embodiments illustrated. On the other hand, it is my intention that all such varia-v tions and modifications as fall within the spirit of the invention be comprehended in the scope of the claims. 3 5

I claim as my invention:

1; In'a hydrocarbon treatment, wherein a hydrocarbon to be treated is contacted with a regenerative contact mass and the contact mass is periodically regenerated by passing a regenerating fluid therethrough, the combination of steps comprising passing a hydrocarbon to be treated through a bed of regenerative contact mass under partial conversion accompanied by a temperature drop is effected,

desire my invention to be limited withdrawing the partially-converted hydrocarbon and adding heat thereto, contacting the heated partially-converted hydrocarbon with a second and larger portion of contact mass whereby further conversion accompanied with a second drop in temperature approximately equal to the first is effected, withdrawing reacted hydrocarbon, and

periodically restoring th efliciency of the contact mass by passing a fiuid regenerating medium through said first bed of contact mass, withdrawing said fluid regenerating medium and with"- drawing heat therefrom, passing said cooled regenerating medium through said second portion of contact mass, withdrawing spent regenerating medium and introducing an oxidizing fluid into said regenerating medium just prior to its contact with each successive bed of contact mass.

2. In an endothermic treatment or conversion of a combustible fiuid material wherein the material to be treated is contacted with a regenerative contact mass at an elevated temperature and a the contact mass is periodically regenerated by oxidizing combustible deposits therefrom, the combination of steps comprising passing the fiuid material to be treated through a bed of regenerative contact mass under treating conditions wherebya partial conversion accompanied by a temperature drop is effected, withdrawing the partially converted material and adding heat thereto, passing the heated partially-converted ,material through a separate and larger portion of contact mass whereby further conversion accompanied by a temperature drop approximately equal to the first is etfected, withdrawing treated material, and periodically restoring theefllciency of the contact mass by passing a fiuid regenerating medium through a bed of said contact, mass, withdrawing said fiuid regenerating medium and withdrawing heat therefrom, passing said cooled regenerating medium through a second portion of said contact mass, withdrawing spent regenerating medium, and introducing an oxidizing fluid capable of oxidizing combustible matter into said regenerating medium 'just prior to its contact with each successive bed of contact mass.

IRVING- I. smmrz.

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